Battery protection system with reference voltage control system

ABSTRACT

A programmable battery protection system. Implementations may include: a battery and a battery protection integrated circuit (IC) coupled with the battery that includes a reference voltage circuit, a variable resistor circuit coupled with the reference voltage circuit, and only two field effect transistors (FETs) coupled with the overcurrent detection circuit and with the battery. The reference voltage circuit and the variable resistor circuit may be configured to cause a current sense signal of the system to vary substantially linearly with changes in a supply voltage of the system.

BACKGROUND

1. Technical Field

Aspects of this document relate generally to battery systems, such asbattery packs for portable electronic devices.

2. Background Art

Battery systems have been devised to allow electronic devices to operateindependent of power from a main power supply. Often, these take theform of a battery pack that contains control circuitry for the batteryand which includes a set of leads which electrically couple the batteryback to the electronic device. Examples of conventional systems anddevices may be found in Japan Patent Application Publication No.P2008-192959A to Masanori Kobayashi, entitled “Semiconductor IntegratedCircuit,” filed Feb. 7, 2007 and published Aug. 21, 2008; JapanesePatent Application Publication No. P2009-131020A to Masatoshi Sugimoto,entitled “Over-Current Protecting Circuit and Battery Pack,” filed Nov.22, 2007 and published Jun. 11, 2009; and Japanese Patent ApplicationPublication No. P2009-283507A to Yamaguchi et al. entitled “VoltageSetting Circuit, Method for Setting Voltage, Secondary BatteryProtecting Circuit, and Semiconductor Integrated Circuit Device,” filedMay 19, 2008 and published Dec. 3, 2009; the disclosures of each ofwhich are hereby incorporated entirely herein by reference.

SUMMARY

Implementations of programmable battery protection systems may include:a battery and a battery protection integrated circuit (IC) coupled withthe battery that includes a reference voltage circuit, a variableresistor circuit coupled with the reference voltage circuit, and onlytwo field effect transistors (FETs) coupled with the overcurrentdetection circuit and with the battery. The reference voltage circuitand the variable resistor circuit may be configured to cause a currentsense signal of the system to vary substantially linearly with changesin a supply voltage of the system.

Implementations of programmable battery protection systems may includeone, all, or any of the following:

The reference voltage circuit and variable resistor circuit may beconfigured to cause an overcurrent signal of the system to besubstantially invariant to changes in a supply voltage of the system.

The reference voltage circuit may include a supply voltage detectorcircuit, a bandgap buffer circuit, and an amplifier operatively coupledtogether.

The variable resistor circuit may include an array of fuses coupled withone or more sets of a plurality of switching components coupled inparallel with one or more sets of a plurality of resistors wherein thestates of the array of fuses may be configured to open or closecorresponding switching components of the one or more sets of theplurality of switching components, permitting one or more summedresistances generated by the one or more sets of the plurality ofresistors to be changed.

The overcurrent detector circuit may be configured to use a referencevoltage generated by the reference voltage circuit to evaluate whether adischarge overcurrent condition or a charging overcurrent conditionexist and to, in response to detecting the discharge overcurrent currentcondition or the charging overcurrent condition, disconnect the only twoFETs from the battery.

The only two FETs and the battery protection IC may be included in thesame semiconductor package.

The states of the array of fuses may be configured to be set using atrimming signal generated during an initial testing of the on resistanceof the only two FETs.

The array of fuses may include polyfuses.

The states of the array of fuses may be configured to be set using alaser trimming signal based on a specified on resistance of the only twoFETs.

The overcurrent detector circuit may be configured to use a referencevoltage generated by the reference voltage circuit and the one or moresummed resistances to evaluate whether a discharge overcurrent conditionor a charging overcurrent condition exist and to, in response todetecting the discharge overcurrent condition and the chargingovercurrent condition, disconnect the only two FETs from the battery.

The battery protection IC may further include a temperature variationcorrection circuit including a diffused resistor coupled to a constantcurrent source and the amplifier. The diffused resistor may beconfigured to change the reference voltage output from the amplifier asa resistance of the diffused resistor changes as a function of thetemperature of the diffused resistor.

The temperature variation correction circuit may be configured to causethe current sense signal of the system to vary substantially linearlywith changes in temperature of the diffused resistor.

Implementations of a battery protection IC for a battery protectionsystem may include a reference voltage circuit including a supplyvoltage detector circuit, a bandgap buffer circuit, and an amplifierwhere the reference voltage circuit may be configured to supply areference voltage that is a function of a supply voltage. A variableresistor circuit may be included and may be coupled with the referencevoltage circuit. The variable resistor circuit may include an array offuses coupled with one or more sets of a plurality of switchingcomponents coupled in parallel with one or more set of a plurality ofresistors. The states of the array of fuses may be configured to open orclose corresponding switching components of the one or more sets of theplurality of switching components, permitting one or more summedresistance generated by the one or more sets of the plurality ofresistors to be changed. An overcurrent detection circuit may be coupledwith the reference voltage circuit and may be configured to use thereference voltage generated by the reference voltage circuit and the oneor more summed resistances to evaluate whether a discharge overcurrentcondition or a charging overcurrent condition exist and to, in responseto detecting the discharge overcurrent condition or the chargingovercurrent condition, disconnect a battery from a load or a charger.

Implementations of a battery protection IC may include one, all, or anyof the following:

A temperature variation correction circuit may be included that mayinclude a diffused resistor coupled to a constant current source and theamplifier where the diffused resistor may be configured to change thereference voltage output from the amplifier as a resistance of thediffused resistor changes as a function of the temperature of thediffused resistor.

Implementations of programmable battery protection systems and batteryprotection ICs may utilize implementations of a method of providing areference voltage to an overcurrent detection circuit of a batteryprotection IC. The method may include substantially linearizing aresponse of a current sense signal of a battery to changes in a supplyvoltage of the battery by using a plurality of states stored in an arrayof fuses to set a summed resistance of a plurality of resistors coupledto a plurality of switching components coupled with the array of fuses.The method may also include, using the summed resistance and a supplyvoltage detector comparator, generating a current by convertingvariation in the supply voltage into a current and, using the currentand a bandgap buffer circuit and an amplifier, generating a referencevoltage for use by an overcurrent detector circuit.

Implementations of a method of providing a reference voltage may includeone, all, or any of the following:

The current may increase when the supply voltage decrease and thecurrent may decrease when the supply voltage increases.

The method may further include using the overcurrent detector circuitand the reference voltage to evaluate whether a discharge overcurrentcondition and a charging overcurrent condition exist and to, in responseto detecting the discharge overcurrent condition or the chargingovercurrent condition, disconnect the battery from a load or a charger.

The method may further include using a temperature variation correctioncircuit to substantially linearize the response of the current sensesignal of the battery to changes in temperature.

The method may further include where the temperature variationcorrection circuit may include a diffused resistor coupled to a constantcurrent source and the amplifier. The method may also include changingthe reference voltage output from the amplifier as a resistance of thediffused resistor changes where the resistance of the diffused resistoris a function of the temperature of the diffused resistor.

The reference voltage may rise as the temperature rises as a function ofthe impedance of the diffused resistor.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a circuit diagram of an first implementation of a battery packsystem;

FIG. 2 is a circuit diagram of a second implementation of a battery packsystem;

FIGS. 3A-C are diagrams of supply voltage versus on resistance of afield effect transistor (FET), supply voltage versus current sourcesignal, and supply voltage versus overcurrent, respectively, for thefirst implementation of a battery pack system of FIG. 1;

FIGS. 4A-C are diagrams of supply voltage versus on resistance of afield effect transistor (FET), supply voltage versus current sourcesignal, and supply voltage versus overcurrent, respectively, for thesecond implementation of a battery pack system of FIG. 2;

FIG. 5 is a circuit diagram of a third implementation of a battery packsystem;

FIGS. 6A-C are diagrams of temperature versus on resistance of a fieldeffect transistor (FET), temperature versus current source signal, andtemperature versus overcurrent, respectively, for the firstimplementation of a battery pack system of FIG. 1;

FIGS. 7A-C are diagrams of temperature versus on resistance of a fieldeffect transistor (FET), temperature versus current source signal, andtemperature versus overcurrent, respectively, for the thirdimplementation of a battery pack system of FIG. 5.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended batteryprotection systems will become apparent for use with particularimplementations from this disclosure. Accordingly, for example, althoughparticular implementations are disclosed, such implementations andimplementing components may comprise any shape, size, style, type,model, version, measurement, concentration, material, quantity, methodelement, step, and/or the like as is known in the art for such, batteryprotection systems and implementing components and methods, consistentwith the intended operation and methods.

Referring to FIG. 1, an implementation of a conventional battery packsystem 2 is illustrated. As illustrated, the system 2 includes a battery4 which generates a supply voltage 6 (VDD, also VCC herein). Anovercurrent detector circuit 8 is included which uses a referencevoltage (threshold voltage) 10 as an input to a discharge overcurrentdetector that includes comparator 12 and variable resistance 14 whichtogether work to detect a discharge overcurrent condition of the battery4. A charging overcurrent detector is also included that has comparator16 and variable resistance 18 that are used to detect a chargingovercurrent condition of the battery. The resistance of variableresistances 14, 18 is set through coupling them with the output of a setof conventional laser trimmed fuses 20, whose values are set duringmanufacturing of the fuses 20 based on an on resistance of field effecttransistors (FETs) 22, 24 that is the manufactured specified value. Thereference voltage 10 is generated using a comparator 26 that receives asits input value, a band gap reference voltage 28. This band gapreference voltage 28 is based on the theoretical band gap of silicon,and may be generated using a wide variety of conventional circuits. Anexample of circuits capable of creating the band gap reference voltage28 are disclosed in the paper by A. Paul Brokaw, entitled “A SimpleThree-Terminal IC Bandgap Reference,” IEEE Journal of Solid-StateCircuits, V. SC-9, No. 6, 388-393 (1974), the disclosure of which ishereby incorporated entirely herein by reference.

The conventional system 2 to outputs the same reference voltage 10 tothe overcurrent detector circuit 8 for detection of overcurrentconditions regardless of the actual supply voltage levels or thetemperatures of the system components, particularly the FETs 22, 24.This behavior, if applied across the entire range of possible supplyvoltage and temperature ranges encountered during operation hasundesirable aspects. Referring to FIG. 3A, it can be observed that theon resistance of the FETs 22, 24 which act to allow electrical power toenter and leave the battery 4 varies as a function of the supply voltageprovided by the battery 4. As can be observed in FIG. 3C, this varianceof the on resistance with the supply voltage results in the overcurrentvalue becoming a function of the supply voltage as well. This conditionis not very desirable, because it means that the ability to detect anovercurrent condition and protect the battery becomes a function of thebattery's own variables, such as charging level, supply voltage,temperature, cell health, etc. The likelihood that the battery will beoperated under undesirable conditions that could damage the battery orcause a safety issue is higher for conventional systems.

Referring to FIG. 2, a second implementation of a battery pack system 30is illustrated. As illustrated, the system 30 includes reference voltagecircuit 32 coupled with a variable resistor circuit 34 and with anovercurrent detection circuit 36. The variable resistor circuit 34includes a fuse array 38 which is coupled to a plurality of resistors 40coupled to the reference voltage circuit 32. Also, as illustrated,various system implementations may also couple the fuse array 38 withvariable resistors/plurality of resistors 42, 44 coupled to comparators46, 48 that are part of the discharge overcurrent and chargingovercurrent detectors of the overcurrent detection circuit 36. Each fusein the fuse array 38 has a certain state (open/closed or left closed)and that state may be set using any of the methods and systems disclosedin copending U.S. patent application Ser. No. 14/809,425, to Saito, etal., entitled “Programmable Battery Protection System and RelatedMethods” filed Jul. 27, 2015; copending U.S. patent application Ser. No.14/811,973 to Saito, et al., entitled “Automatically ProgrammableBattery Protection System and Related Methods,” filed Jul. 29, 2015; andcopending U.S. patent application Ser. No. 14/813,314, to Amemiya, etal., entitled “Automatically Programmable Battery Protection System andRelated Methods,” filed Jul. 30, 2015 (the “Fuse-Related Applications”),the disclosures of each of which are hereby incorporated entirely hereinby reference. In particular implementations, the fuses may be set usinglaser trimming using a specified on resistance for the FETs 66, 68rather than the methods disclosed in the Fuse-Related Applications. Thefuses 38 may be polyfuses in particular implementations. The variouscomponents of the system that do not include the FETs 66, 68 areincluded in a battery protection integrated circuit (IC) which isphysically separate from the battery itself. In various implementations,the battery protection IC may be included with the FETs in the samesemiconductor package.

In various system implementations, the array of fuses 38 are coupled toa plurality of switching components (not shown) that are coupled inparallel with a plurality of resistors 40 that are coupled in series. Asdescribed at length in the Fuse-Related Applications, as the switchingcomponents are individually opened or closed, a summed resistance of theplurality of resistors 40 changes, which changes the ultimate voltagethat remains and current that passes through the plurality of resistors40. The switching components that are opened or closed depend on thestates of the corresponding fuses in the array of fuses 38. A widevariety of switching components may be utilized in variousimplementations including any disclosed in the Fuse-Related Applicationsor disclosed in the various references incorporated by reference in thisdocument. As illustrated in FIG. 2, the array of fuses 38 can alsoinclude fuses used to set the summed resistance of variable resistors42, 44. In implementations where the variable resistors 42, 44 alsoinclude a plurality of resistors and plurality of switching components,the array of fuses 38 may be coupled to more than one set of a pluralityof resistors and more than one set of a plurality of switchingcomponents. The same fuse states may be used to set the summedresistance of the plurality of resistors 40 and the variable resistors42, 44, or the fuse array 38 may include separate portions of fuseswhich are used to set the summed resistance for each set of plurality ofresistors individually, or in any particular combination.

The summed resistance of the plurality of resistors 40 is used togenerate a current signal as the supply voltage changes. By using thiscurrent signal, a current sense signal of the system can be made to varysubstantially linearly with changes in the supply voltage. Also, becausechanges in the supply voltage can be comprehended, the overcurrentsignals (via the reference voltages used) can be made substantiallyinvariant to changes in the supply voltage. Non-limiting examplessufficient to inform those of ordinary skill in the art of substantiallylinear relationships between current sense and supply voltage (Vcc) andsubstantially invariant relationships between overcurrent and supplyvoltage can be found in FIGS. 4A and 4C, respectively.

Referring to FIG. 2, the supply voltage (VCC) is supplied to comparator50, which is designed to output a voltage when the supply voltagechanges and to not output a voltage when the supply voltage remainsconstant (comparative supply voltage 60) through connecting the outputof the comparator 50 to the negative terminal of the comparator 50. Theplurality of resistors 40 then create a current in combination withconstant current source 52 included in a band gap buffer circuit thatincludes a comparator 54. Comparator 54 compares a band gap voltage VBGZwith the voltage present in the circuit including the constant currentsource 52 and outputs a voltage that opens the gates of two transistorsto create a differential voltage 62 to be input into amplifier 56.Amplifier 56 then outputs the reference voltage 58 which is thensupplied to comparators 46 and 48 for use in detecting overcurrentconditions.

By varying the summed resistance of the plurality of resistors 40, thedifferential voltage 62 applied to the amplifier 56 can be adjusted.Also, because the current generated using the comparative supply voltage60 varies depending on changes in the supply voltage, the differentialvoltage 62 changes as well, which allows the reference voltage 58 to bedynamically/automatically changed during operation as a function of theactual supply voltage. By inspection of the circuit diagram, the CS(current sense) signal is also a function of the reference voltage 58,and will vary as the reference voltage 58 varies. Since the referencevoltage 58 is a function of changes in the supply voltage, the currentsense signal is now also a function of changes in the supply voltage. Bybeing able to program/set the value of the summed resistance of theplurality of resistors 40 following assembly of the system 30 duringinitial testing using a testing fuse trimming signal 64, for example,the actual on resistances of the FETs 66, 68 can be calculated. Asdiscussed in the Fuse-Related Applications, the ability to adjust theparameters of the system based on the actual on resistance of the FETs66, 68 may reduce the variability in the reference voltage 58 andimprove protection of the battery and mitigate unsafe operatingconditions. Combining this capability with the ability to dynamicallyadjust the reference voltage 58 based on changes in the supply voltagemay further reduce variability in the reference voltage 58 and therebyimprove system operation and safety.

Examples of the operating characteristics of an implementation of abattery pack system like that illustrated in FIG. 2 are illustrated inFIGS. 4A-C. FIG. 4A demonstrates that the on resistance of the FETs isstill the same function of the supply voltage as in the implementationsillustrated in FIG. 1 and FIG. 3A. FIG. 4B, however, illustrates how thecurrent sense signal is a substantially linear function of the supplyvoltage. Since the slope of the line is negative, when the supplyvoltage increase, the current sense signal (and current) goes down; whenthe supply voltage decreases, the current sense signal (and current)goes up. The effect of this linearization and ability to dynamicallyadjust the reference voltage 58 during operation to changes in supplyvoltage can be seen in FIG. 4C, which shows how the overcurrent signalhas become substantially invariant to changes in the supply voltage.

Referring to FIG. 5, a third implementation of a battery pack system 70is illustrated. As illustrated, the reference voltage 72 of the system70 is generated by a temperature variation correction circuit 84. Thecircuit 84 includes an amplifier 74 which receives an input voltage 86from a constant current source 76 coupled to ground through a diffusedresistor 78. The resistance of diffused resistor 78 is a function of thetemperature of the resistor 78, because the impedance of the resistor 78changes with temperature. Because of this, as the temperature of thediffused resistor 78 changes, the input voltage 86 to the amplifier 74also changes. Examples of diffused resistors that may be used in variousimplementations may be found in the paper by Chuang et al., entitled“Temperature-dependent Characteristics of Polysilicon and DiffusedResistors,” IEEE Transactions on Electron Devices, V. 50, No. 5, p.1413-1415 (May 2003), the disclosure of which is incorporated entirelyherein by reference.

Since the temperature of the resistor 78 is likely to be very close tothe temperature of the battery protection IC, and where the FETs 80, 82and the battery protection IC are included in the same package (as theyare in various implementations), the temperature of the resistor 78 isalso likely to be very close to the temperature of the FETs 80, 82. Thisis significant, because the on resistance of the FETs 80, 82 is afunction of their temperature. Accordingly, being able to use thetemperature of the diffused resistor 78 as an input to the referencevoltage circuit 84 generating the reference voltage 72 provides a way tochange the reference voltage 72 as a function of the temperaturedependence of the on resistance of one or both FETs 80, 82.

As illustrated, an array of fuses 88 may be used to set the resistanceof variable resistors 90, 92 as previously disclosed herein. In suchimplementations, the use of a reference voltage circuit 32 like thosedisclosed herein may not be used. In other implementations, a referencevoltage circuit 32 like those disclosed herein may be used incombination with the temperature variation correction circuit 84. Insuch implementations, the effects of variation of the on resistance ofthe FETs with both supply voltage and temperature may be able to bedynamically controlled and reflected in the threshold voltage suppliedto the overcurrent detection circuit. In other implementations, eithercircuit 32, 84 could be used independently to control supply voltageeffects or temperature effects as desired.

Referring to FIGS. 6A-C and 7A-C, the characteristics of the system 2implementation illustrated in FIG. 1 and the characteristics of thesystem 70 illustrated in FIG. 5 are illustrated, respectively. FIG. 6Ashows how the on resistance (Rsson) of the FETs 22, 24 varies as afunction of the temperature of the FETs. Since the FETs 80, 82 in thesystem of 70 are the same, they show the same temperature behavior asillustrated in FIG. 7A. By inspection, it is evident that there is nocorrelation between the current sense signal and the temperature of theFETs for the system 2. However (see FIG. 7B), through the use of thetemperature variation correction circuit 84, the current sense signalvaries substantially linearly with changes in temperature of the FETs80, 82 (since the diffused resistor 78 is close to the FETs 80, 82, itis accurate to say the variation is with respect to the temperature ofthe diffused resistor 78 as well). Since the slope of the line in FIG.7B is positive, increases in temperature increase the current sensesignal and vice versa. The change in current sense signal reflects thechange in impedance in the diffused resistor 78 as the temperaturerises, increasing the impedance. The reference voltage 72 likewisechanges with the impedance of the diffused resistor 78, increasing asthe impedance increases.

Using the various reference voltages disclosed herein, the variousovercurrent detection circuits disclosed herein determine whether adischarge overcurrent condition and/or charging overcurrent conditionexists with respect to the battery being connected to a load or to acharger, respectively. If either or both conditions are detected, theovercurrent detection circuits are configured to disconnect the batterypack system from the load or charger to prevent damage to the batteryand/or the load or charger.

In places where the description above refers to particularimplementations of battery protection systems and implementingcomponents, sub-components, methods and sub-methods, it should bereadily apparent that a number of modifications may be made withoutdeparting from the spirit thereof and that these implementations,implementing components, sub-components, methods and sub-methods may beapplied to other battery protection systems.

What is claimed is:
 1. A programmable battery protection systemcomprising: a battery; and a battery protection integrated circuit (IC)coupled with the battery comprising: a reference voltage circuit; avariable resistor circuit coupled with the reference voltage circuit;and an overcurrent detection circuit coupled with the reference voltagecircuit; and only two field effect transistors (FETs) coupled with theovercurrent detection circuit and with the battery; wherein thereference voltage circuit and variable resistor circuit are configuredto cause a current sense signal of the system to vary substantiallylinearly with changes in a supply voltage of the system.
 2. The systemof claim 1, wherein the reference voltage circuit and variable resistorcircuit are configured to cause an overcurrent signal of the system tobe substantially invariant to changes in a supply voltage of the system.3. The system of claim 1, wherein the reference voltage circuitcomprises a supply voltage detector circuit, a bandgap buffer circuit,and an amplifier operatively coupled together.
 4. The system of claim 1,wherein the variable resistor circuit comprises an array of fusescoupled with one or more sets of a plurality of switching componentscoupled in parallel with one or more sets of a plurality of resistorswherein the states of the array of fuses are configured to open or closecorresponding switching components of the one or more sets of theplurality of switching components, permitting one or more summedresistances generated by the one or more sets of the plurality ofresistors to be changed.
 5. The system of claim 1, wherein theovercurrent detector circuit is configured to use a reference voltagegenerated by the reference voltage circuit to evaluate whether one of adischarge overcurrent condition and charging overcurrent condition existand to, in response to detecting the one of the discharge overcurrentcondition and the charging overcurrent condition, disconnect the onlytwo FETs from the battery.
 6. The system of claim 1, wherein the onlytwo FETs and the battery protection IC are comprised in the samesemiconductor package.
 7. The system of claim 4, wherein the states ofthe array of fuses are configured to be set using a trimming signalgenerated during an initial testing of the on resistance of the only twoFETs.
 8. The system of claim 4, wherein the array of fuses comprisepolyfuses.
 9. The system of claim 4, wherein the states of the array offuses are configured to be set using a laser trimming signal based on aspecified on resistance of the only two FETs.
 10. The system of claim 4,wherein the overcurrent detector circuit is configured to use areference voltage generated by the reference voltage circuit and the oneor more summed resistances to evaluate whether one of a dischargeovercurrent condition and a charging overcurrent condition exist and to,in response to detecting the one of the discharge overcurrent conditionand the charging overcurrent condition, disconnect the only two FETsfrom the battery.
 11. The system of claim 1, wherein the batteryprotection IC further comprises a temperature variation correctioncircuit comprising a diffused resistor coupled to a constant currentsource and the amplifier, wherein the diffused resistor is configured tochange the reference voltage output from the amplifier as a resistanceof the diffused resistor changes as a function of the temperature of thediffused resistor.
 12. The system of claim 11, wherein the temperaturevariation correction circuit is configured to cause the current sensesignal of the system to vary substantially linearly with changes intemperature of the diffused resistor.
 13. A battery protectionintegrated circuit (IC) for a battery protection system, the circuitcomprising: a reference voltage circuit comprising a supply voltagedetector circuit, a bandgap buffer circuit, and an amplifier, thereference voltage circuit configured to supply a reference voltage thatis a function of a supply voltage; a variable resistor circuit coupledwith the reference voltage circuit, the variable resistor circuitcomprising an array of fuses coupled with one or more sets of aplurality of switching components coupled in parallel with one or moresets of a plurality of resistors wherein the states of the array offuses are configured to open or close corresponding switching componentsof the one or more sets of the plurality of switching components,permitting one or more summed resistances generated by the one or moresets of the plurality of resistors to be changed; and an overcurrentdetection circuit coupled with the reference voltage circuit; whereinthe overcurrent detector circuit is configured to use the referencevoltage generated by the reference voltage circuit and the one or moresummed resistances to evaluate whether one of a discharge overcurrentcondition and charging overcurrent condition exist and to, in responseto detecting the one of the discharge overcurrent condition and thecharging overcurrent condition, disconnect a battery from one of a loadand a charger.
 14. The IC of claim 13, further comprising a temperaturevariation correction circuit comprising a diffused resistor coupled to aconstant current source and the amplifier, wherein the diffused resistoris configured to change the reference voltage output from the amplifieras a resistance of the diffused resistor changes as a function of thetemperature of the diffused resistor.
 15. A method of providing areference voltage to an overcurrent detection circuit of a batteryprotection integrated circuit (IC), the method comprising: substantiallylinearizing a response of a current sense signal of a battery to changesin a supply voltage of the battery by: using a plurality of statesstored in an array of fuses, setting a summed resistance of a pluralityof resistors coupled to a plurality of switching components coupled withthe array of fuses; using the summed resistance and a supply voltagedetector comparator, generating a current by converting variation in thesupply voltage into a current; and using the current and a bandgapbuffer circuit and an amplifier, generating a reference voltage for useby an overcurrent detector circuit.
 16. The method of claim 15, whereinthe current increases when the supply voltage decreases and the currentdecreases when the supply voltage increases.
 17. The method of claim 15,further comprising using the overcurrent detector circuit and thereference voltage to evaluate whether one of a discharge overcurrentcondition and a charging overcurrent condition exist and to, in responseto detecting the one of the discharge overcurrent condition and thecharging overcurrent condition, disconnect the battery from one of aload and a charger.
 18. The method of claim 15, further comprising usinga temperature variation correction circuit to substantially linearizethe response of the current sense signal of the battery to changes intemperature.
 19. The method of claim 18, wherein the temperaturevariation correction circuit comprises a diffused resistor coupled to aconstant current source and the amplifier, and wherein the methodfurther comprises changing the reference voltage output from theamplifier as a resistance of the diffused resistor changes where theresistance of the diffused resistor is a function of the temperature ofthe diffused resistor.
 20. The method of claim 19, wherein the referencevoltage rises as the temperature rises as a function of the impedance ofthe diffused resistor.